Process for obtaining a photographic image with improved image-tone according to thesilver halide diffusion transfer process



, do not undergo any further change.

United States Patent PRGCESS FOR GBTAWING A PHQTGGWHE EMAGE WHTH IMPROVED HVEAGE-TQNE AC- CQRDHNG TO THE SHLVER HALKDE DIFFUSIQN TRANSFER PRQCESS y Jozef Frans Willems and Gerard Michiel Sevens, Wilriik- Antwerp, and Louis Maria De Haes, Edegern-Antwerp, Belgium, assiwors to Gevaert Photo-Producten N.V., Mortsel, Belgium, :1 Belgian company No Drawing. Filed Nov. 6, 1961, tier. No. 150,173 Claims priority, application Belgium Nov. 8, 1961) 12 Claims. (Cl. 96-29) This invention relates to the obtaining of black or bluish blaclgimage tones according to the photographic silver complex diffusion transfer process.

According to the known silver complex dilfusion transfer processes, the principle of whichlis described in our British patent specifications 614,155 and 654,630, and in the German patent specification 887,733, a light-sensitive silver halide emulsion layer is exposed to an image 1 and then developed into contactwith specially pretreated receiving material in the presence of a silver halide solvent. The exposed areas of the image are developed and The undeveloped silver halide present in the unexposed areas is dissolved by the silver halide solvent which is present either inthe developer or in the receiving layer, transferred by diifusion into the receiving layer of the said receiving material and converted therein to metallic silver.

This conversion is promoted by the catalytic. action of developing nuclei which are present. These nuclei normally consist of finely divided metal or metal sulfide. In this Way, a positive image of the original is formed in the receiving layer and is apparent after separation of the latter from the emulsion layer.

Besides the classical development with an organic re ducing agent in the presence of photochemical nuclei, metal sulfides such as zinc sulfide can also develop the transferred silver complex in the receiving layer into a silver sulfide image.

A disadvantage of the silver complex diffusion transfer process is the less agreeable brown image-tone of the obtained silver image in the finished image-receiving material.

It has now been found that a black or a bluish-black image-tone is obtained when using in the above-mentioned processes an imidazolidine-4-thione with the following general tautorneric formula:

wherein: each of R R R R represents a hydrogen atom, an alkyl radical, a substituted alkyl radical, an aryl radical or a substituted aryl radical,e.g., an alkaryl radical, or wherein R and R and also R and R two by two represent the atoms necessary for closing a saturated homocyclic ring or a substituted homocyclic ring.

Some compounds of this type which form the experiments appeared to be particularly suited for being applied in the process according identified below:

Inc

I CH2 The preparation for the greater part corresponds with the reaction of ketone cyanohydrines with ammonium sulfide. V

The black-toningagent, according to this invention to the present invention, are.

ably between 10 and 50 mg. of black-toning agent according to this invention. i

When the black-toning agentaccording to this invention is added to the developing solution, the concentration of imidazolidine-4-thione derivative is preferably chosen between 0.05 g. and 5 g. per liter of developing solution. If the black-toning agent is added to the silver halide emulsion layer, the concentration is preferably chosen between 0.02 g. and 1- gram per kg. of flowable emulsion. The image-receiving layer is coated onto a support preferably a paper support. On the image-receiving layer a surface layer may be present as described in our BelgianPatent Numbers 609,394 and 609,395.

So the image receiving layer makes part of a bi-pack material. Onto the receiving layer a silver halide emul-,

sion layervis coated. In the latter case the image receiving layer is hardened and the silver halide, emulsion layer is either unhardened or little hardened.

After exposure, development and diffusion transfer, the exposed and developed silver halide emulsion layer is removed, e.g., by washing with warm Water.

The developing substance used for developing the lightsensitive material, may be present either in the silver halide emulsion layer, in the alkaline developing solution, or in both. Mixtures of developing substances may also be considered.

The complexing agent forming. a soluble complex with silver halide, preferably consists of sodium thiosulfate and may be added to the image-receiving layer as well as to the bath. 7 v

In order to avoid fogging in the exposed silver halide emulsion layers it is in many cases favorable to use a fog inhibiting compound. This fog inhibiting compound may be added either to the silver halide emulsion or to the bath. Besides the classically used fog inhibiting compounds, the imidazolidine-4-thiones are also suited for this purpose. V

The following examples illustrate the invention without limiting, however, the scope thereof.

Example 1 A solution of 250 mg. of 2,2,5,5-tetramethyl imidazolidine- 4-thione in orm' of ethanol is added to 1 kg of gelatino silver chloro. iodide emulsion ready for coating and containing 0.5% by weight of iodide. For prean original to be reproduced, and then passed through 1 a developing bath together with a paper provided with an image-receiving layer comprising a binding agent and developing nuclei. The developing bath comprises hydroquinone, l-phenyl-i-pyrazolidone and sodium thiosulfate. On leaving the developing bath, both layers are squeezed into contact witheach other and after a 10 to 20 seconds separated again. In the receiving-layer an image of the originalis obtained with a markedly black image tone.v

When, however, in a similar method no .use is made of the aforesaid black-toning agent, images with a disagreeable yelloW-brown image tone are obtained.

Example 2 400 cm? of a 1% alcoholic solution of 2,2,5-trimeth'yl imidazolidine-4-thione are added to 1 kg. of a gelatino Example 3 A paper support is coated with an image-receiving layer from a' suspension of the following composition:

Water cm. 274 Gelatin g-- 10 Sodium. thiosulfate g 12 Sodium sulfide .mol 7.7)(10- Cobaltous nitrate 6 aq. mol 1.1 10- 1% alcoholic solution of 2,2,5,5-tetramethyl imidazoline-4-thi-one ..cm. 17

With :1 1. solution 13 sq. m. paper surface are cov red. This image-receiving layer in its term is coated with a layer from a solution consisting of :v

4% aqueous solution of carboxymethyl cellulose 45 Water 155 Sandozol (trade name for a sulfonated organic oil marketed by Sandoz, A.G., Basel, Switzerland) 0.6

A silver halide emulsion paper as used in Example 1, containing, however, no 2,2,5,5-tetramethylimidazolidine-4-thione, after exposure in contact with an original to be reproduced is developed in a solution of thefollowing composition:

Water cm. 1.000 Sodium sulfite I g Sodium hydroxide g 10 Potassium bromide g 1 Hydroquinone g 16 l-phenyl-3-pyrazolidone g 1 On leaving the developing bath the emulsion layer of this material is pressed into contact with the image,

receiving layer of the above describedmaterialandsepa-' rated therefrom after 10-20 sec. 7 p

In comparison with the image-tone of a material containing no-black-toning agent, the image-tone obtained in thisimage-receiving layer shows a more neutral co or.

- Example 4 Example 3 is repeated after having substituted, however in the image-receiving layer a same amount of 2,2,5- trimethyl imidazolidinei-thione for the 2,2,5,5-tetramethyl imidaz0lidine-4-thione.

In comparison with'the image-tone of a, material containing no black-toning agent, the image-tone obtained in this receiving layer shows a more neutral color.

Example 5 an image of the original is obtained which shows a more neutral black image-tone.

Example 6 Example 5 is repeated, substituting, however, 1 g. of 2,2,5-tr-imethyl imidazolidine-4-thione for the same amount of 2,2,5,5,-tetramethyl imidazolidine-4-tbione. In the image-receiving layer an image of the original is formed which shows a more neutral image-tone.

We claim:

1. A process for preparing a photographic image which comprises exposing a photographic silver halide emulsion layer to a subject, developing the emulsion layer, then transferring the silver halide by diffusion from the undeveloped areas of the emulsion layer to an image-receiving layer, the transfer being effected in contiguity with a silver halide solvent and at least one imidazolidinel-thione compound having the following tautomeric formula:

wherein each of R R R and R is a member selected from the group consisting of a hydrogen atom, and alkyl radical, and an aryl radical.

2. A process for preparing a photographic image which comprises exposing a photographic silver halide emulsion layer to a subject, developing the emulsion layer, then transferring the silver halide by diffusion from the undeveloped areas of the emulsion layer to an image-receiving layer, the transfer being effected in contiguity with a silver halide solvent and at least one imidazolidine-4-thione compound having the following tautomeric formula:

wherein each of X and Y are the necessary atoms to form a cycloaliphatic ring structure.

3. A process for preparing a photographic image which comprises exposing a photographic silver halide emulsion layer to a subject, developing the emulsion layer, then transferring the silver halide by diffusion from the undeveloped areas of the emulsion layer to an image-receiving layer, the transfer being effected in contiguity with a 5 silver halide solvent and at least one imidaZolidinel-thione compound having the following tautomeric formula:

4. A process according to claim 1, wherein the imidazolidine-4-thione compound is present in the image-receiving material.

5. A process according to claim 2, wherein the imidazolidine-4-thione compound is present in the image-receiving material.

6. A process according to claim 3, wherein the imidazolidinel-thione compound is present in the image-receiving material.

7. A process according to claim 1, wherein the imidazolidine-4-thione compound is present in the treating liquid.

8. A process according to claim 2, wherein the imidazolidine-4-thione compound is present in the treating liquid. 7

9. A process according to claim 3, wherein the imidazolidine-4-thione compound is present in the treating liquid.

10. A process according to claim 1, wherein the imidazolidine-4-thione compound is present in the light sensitive material.

11. A process according to claim 2, wherein the imidazolidine-4-thione compound is present in the light sensitive material. r

12. A process according to claim 3, wherein the imidazolidine-4-thione compound is present in the light sensitive material.

References Cited in the file of this patent UNITED STATES PATENTS 2,785,175 Christian Mar. 12, 1957 2,806,306 Christian Sept. 10, 1957 3,017,270 Tregillus Jan. 16, 1962 FOREIGN PATENTS 595,695 Belgium Feb. 1, 1961.

217,057 Australia Sept. 11, 1961 OTHER REFERENCES Photo Science and Eng. 4. No. 5 (1960), pp. 257-263. Glafkides: Photographic Chemistry, 1 Fountain Press, andQ pp- 380. 

1. A PROCESS FOR PREPARING A PHOTOGRAPHIC IMAGE WHICH COMPRISES EXPOSING A PHOTOGRAPHIC SILVER HALIDE EMULSION LAYER TO A SUBJECT, DEVELOPING THE EMULSION LAYER, THEN TRANSFERRING THE SILVER HALIDE BY DIFFUSION FROM THE UNDEVELOPED AREAS OF THE EMULSION LAYER TO AN IMAGE-RECEIVING LAYER, THE TRANSFER BEING EFFECTED IN CONTIGUITY WITH A SILVER HALIDE SOLVENT AND AT LEAST ONE IMIDAZOLIDINE-4-THIONE COMPOUND HAVING THE FOLLOWING TAUTOMERIC FORMULA: 